1. Field of the Invention
The present invention relates to a communication control system, and more particularly to a communication control system having architecture for rescuing the system from a fault.
2. Description of the Related Art
Recently, a variety of services has been provided through a communication network using two-wire or four-wire metallic cables. Examples of the above services are POTS (Plain Old Telephone Service) that provides only the conventional voice communication service, and high-speed digital transmission service such as ISDN or xDSL (Digital Subscriber Line) service. Nowadays, there is a demand for a variety of different services that enable subscribers to have different operation styles and different transmission formations.
With regard to the above demand, a necessity of a subscriber termination unit in which different types of communication packages that match different transmission formations comes out from economical efficiency on the office side.
If it is considered that the above-mentioned subscriber termination unit having different types of communication packages is rescued from a fault that may occur in any of these packages, each of the communication packages will be doubled so as to form a redundant system for each of the different transmission formations (or each of the subscribers). However, the redundant system would decrease the number of lines that can be accommodated by the subscriber termination unit.
A redundant package for rescue may be provided for each of the different transmission formations. In this case, an N:1 redundant system including N communication packages and a single rescue package is configured. Wiring lines would be fixedly laid on a backboard of a housing of the subscriber termination unit. However, this would prevent the system from being rescued efficiently.
The following is assumed in order to describe the above redundant system in more detail. The subscriber termination unit is equipped with three types of communication packages that match transmission formation A, transmission formation B and transmission formation C, respectively. Wires are laid on the backboard of the housing of the subscriber termination unit in such a way as to assign a single rescue package to each of the three transmission formations. Thus, the N:1 redundant system is formed for each of the three transmission formations.
In the case thus assumed, if one of the communication packages involved in the transmission formation A fails to operate properly, the subscriber termination unit can be rescued by using the rescue package for the transmission formation A. However, if another communication package of the transmission formation A fails to operate properly, the system will be no longer rescued because no rescue package for the transmission formation A is available. The rescue packages of the transmission formations B and C cannot be used for rescue, because these rescue packages are fixedly connected to the communication packages of the transmission formations B and C.
As described above, the conventional arrangement of the rescue packages is not adaptive to the situation in which a fault occurs, and therefore the subscriber termination unit cannot be efficiently rescued.
Taking the above into consideration, an object of the present invention is to provide a communication control system capable of rescuing a unit equipped with communication packages of different transmission systems efficiently and economically if a fault has occurred in any of these communication packages.
To accomplish the above object, according to the present invention, there is provided a communication control system having a rescue architecture comprising: a rescue bus connected to units in a multiple formation; switch parts each including a line switch, a rescue bus connection switch and a rescue switch, the line switch connecting a signal in a channel on a line and a signal processing part that processes the signal in normal operation and disconnecting the signal from the signal processing part when a fault has occurred, the rescue bus connecting switch connecting the line and the rescue bus when the fault has occurred, the rescue switch connecting the rescue bus and a backup signal processing part that processes the signal instead of a faulty unit that is one of the units in which the fault has occurred; at least one communication unit including one of the switch parts and the signal processing part; a rescue unit including another one of the switch parts and the backup signal processing part and performing at least one of a complete rescue based on a unit basis and a provisional rescue based on a channel basis; and a monitor control device monitoring occurrence of a fault and perform switch control of the switch parts.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.